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Yersinia pestis endowed with increased cytotoxicity is avirulent in a bubonic plague model and induces rapid protection against pneumonic plague.

Zauberman A, Tidhar A, Levy Y, Bar-Haim E, Halperin G, Flashner Y, Cohen S, Shafferman A, Mamroud E - PLoS ONE (2009)

Bottom Line: Following subcutaneous infection, this strain had reduced ability to colonize internal organs, was unable to induce septicemia and exhibited at least a 10(7)-fold reduction in virulence.Yet, upon intravenous or intranasal infection, it was still as virulent as the wild-type strain.These observations have novel implications for the development of vaccines/therapies against Y. pestis and shed new light on the virulence strategies of Y. pestis in nature.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona, Israel.

ABSTRACT
An important virulence strategy evolved by bacterial pathogens to overcome host defenses is the modulation of host cell death. Previous observations have indicated that Yersinia pestis, the causative agent of plague disease, exhibits restricted capacity to induce cell death in macrophages due to ineffective translocation of the type III secretion effector YopJ, as opposed to the readily translocated YopP, the YopJ homologue of the enteropathogen Yersinia enterocolitica Oratio8. This led us to suggest that reduced cytotoxic potency may allow pathogen propagation within a shielded niche, leading to increased virulence. To test the relationship between cytotoxic potential and virulence, we replaced Y. pestis YopJ with YopP. The YopP-expressing Y. pestis strain exhibited high cytotoxic activity against macrophages in vitro. Following subcutaneous infection, this strain had reduced ability to colonize internal organs, was unable to induce septicemia and exhibited at least a 10(7)-fold reduction in virulence. Yet, upon intravenous or intranasal infection, it was still as virulent as the wild-type strain. The subcutaneous administration of the cytotoxic Y. pestis strain appears to activate a rapid and potent systemic, CTL-independent, immunoprotective response, allowing the organism to overcome simultaneous coinfection with 10,000 LD(50) of virulent Y. pestis. Moreover, three days after subcutaneous administration of this strain, animals were also protected against septicemic or primary pneumonic plague. Our findings indicate that an inverse relationship exists between the cytotoxic potential of Y. pestis and its virulence following subcutaneous infection. This appears to be associated with the ability of the engineered cytotoxic Y. pestis strain to induce very rapid, effective and long-lasting protection against bubonic and pneumonic plague. These observations have novel implications for the development of vaccines/therapies against Y. pestis and shed new light on the virulence strategies of Y. pestis in nature.

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Y. pestis Kim53ΔJ+P strain confers prolonged protection against plague.(A) Mice (7–8 per group) were infected subcutaneously with 1×105 cfu of Kim53ΔJ+P (circle); EV76 (× symbol); or EV76ΔJ+P (triangle). Control animals were treated with saline (square). Animals were bled for ELISA determination of anti-F1 antibody titers 45 days following immunization. Titers following immunization with Kim53ΔJ+P ranged from 64,000 to 100,000, with GMT of 18,500, while titers for the EV76 or EV76ΔJ+P immunized animals ranged from 640 to less than 10, with GMT of 30 and 10, respectively. Animals were challenged subcutaneously with 1×103 cfu (∼1×103 LD50) of Y. pestis Kim53 (panel A) or intranasally with 8×103 cfu (∼15 LD50) of Y. pestis Kim53 (panel B).
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pone-0005938-g005: Y. pestis Kim53ΔJ+P strain confers prolonged protection against plague.(A) Mice (7–8 per group) were infected subcutaneously with 1×105 cfu of Kim53ΔJ+P (circle); EV76 (× symbol); or EV76ΔJ+P (triangle). Control animals were treated with saline (square). Animals were bled for ELISA determination of anti-F1 antibody titers 45 days following immunization. Titers following immunization with Kim53ΔJ+P ranged from 64,000 to 100,000, with GMT of 18,500, while titers for the EV76 or EV76ΔJ+P immunized animals ranged from 640 to less than 10, with GMT of 30 and 10, respectively. Animals were challenged subcutaneously with 1×103 cfu (∼1×103 LD50) of Y. pestis Kim53 (panel A) or intranasally with 8×103 cfu (∼15 LD50) of Y. pestis Kim53 (panel B).

Mentions: Certain characteristics of Kim53ΔJ+P-induced resistance are reminiscent of the cross-priming mechanism of CD8 T cell activation [36]–[38]. To examine the involvement of CD8 T cells in the protective mechanism induced by Kim53ΔJ+P, C57BL/6J mice and their isogenic strain deleted for class I MHC genes (KbDb−/−) were infected subcutaneously with the virulent Kim53pGFP or the cytotoxic Kim53ΔJ+P strain (Figure 5E). All mice infected with Kim53ΔJ+P survived the infection, whereas all mice infected with Kim53pGFP died. This finding indicated that the observed attenuation of the cytotoxic strain is not a result of a cross-priming mechanism and CD8 T cell activation. In addition, inflammatory processes in the spleen did not seem to account for the rapid development of systemic protection, since no significant differences could be demonstrated between the levels of pro-inflammatory cytokines (TNF-α and IL-6) and Th1 cytokines (IFN-γ, IL-2 and IL-12) at 36, 60 and 72 hours post infection with Kim53ΔJ+P or Kim53pGFP (data not shown).


Yersinia pestis endowed with increased cytotoxicity is avirulent in a bubonic plague model and induces rapid protection against pneumonic plague.

Zauberman A, Tidhar A, Levy Y, Bar-Haim E, Halperin G, Flashner Y, Cohen S, Shafferman A, Mamroud E - PLoS ONE (2009)

Y. pestis Kim53ΔJ+P strain confers prolonged protection against plague.(A) Mice (7–8 per group) were infected subcutaneously with 1×105 cfu of Kim53ΔJ+P (circle); EV76 (× symbol); or EV76ΔJ+P (triangle). Control animals were treated with saline (square). Animals were bled for ELISA determination of anti-F1 antibody titers 45 days following immunization. Titers following immunization with Kim53ΔJ+P ranged from 64,000 to 100,000, with GMT of 18,500, while titers for the EV76 or EV76ΔJ+P immunized animals ranged from 640 to less than 10, with GMT of 30 and 10, respectively. Animals were challenged subcutaneously with 1×103 cfu (∼1×103 LD50) of Y. pestis Kim53 (panel A) or intranasally with 8×103 cfu (∼15 LD50) of Y. pestis Kim53 (panel B).
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2691952&req=5

pone-0005938-g005: Y. pestis Kim53ΔJ+P strain confers prolonged protection against plague.(A) Mice (7–8 per group) were infected subcutaneously with 1×105 cfu of Kim53ΔJ+P (circle); EV76 (× symbol); or EV76ΔJ+P (triangle). Control animals were treated with saline (square). Animals were bled for ELISA determination of anti-F1 antibody titers 45 days following immunization. Titers following immunization with Kim53ΔJ+P ranged from 64,000 to 100,000, with GMT of 18,500, while titers for the EV76 or EV76ΔJ+P immunized animals ranged from 640 to less than 10, with GMT of 30 and 10, respectively. Animals were challenged subcutaneously with 1×103 cfu (∼1×103 LD50) of Y. pestis Kim53 (panel A) or intranasally with 8×103 cfu (∼15 LD50) of Y. pestis Kim53 (panel B).
Mentions: Certain characteristics of Kim53ΔJ+P-induced resistance are reminiscent of the cross-priming mechanism of CD8 T cell activation [36]–[38]. To examine the involvement of CD8 T cells in the protective mechanism induced by Kim53ΔJ+P, C57BL/6J mice and their isogenic strain deleted for class I MHC genes (KbDb−/−) were infected subcutaneously with the virulent Kim53pGFP or the cytotoxic Kim53ΔJ+P strain (Figure 5E). All mice infected with Kim53ΔJ+P survived the infection, whereas all mice infected with Kim53pGFP died. This finding indicated that the observed attenuation of the cytotoxic strain is not a result of a cross-priming mechanism and CD8 T cell activation. In addition, inflammatory processes in the spleen did not seem to account for the rapid development of systemic protection, since no significant differences could be demonstrated between the levels of pro-inflammatory cytokines (TNF-α and IL-6) and Th1 cytokines (IFN-γ, IL-2 and IL-12) at 36, 60 and 72 hours post infection with Kim53ΔJ+P or Kim53pGFP (data not shown).

Bottom Line: Following subcutaneous infection, this strain had reduced ability to colonize internal organs, was unable to induce septicemia and exhibited at least a 10(7)-fold reduction in virulence.Yet, upon intravenous or intranasal infection, it was still as virulent as the wild-type strain.These observations have novel implications for the development of vaccines/therapies against Y. pestis and shed new light on the virulence strategies of Y. pestis in nature.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research, Ness-Ziona, Israel.

ABSTRACT
An important virulence strategy evolved by bacterial pathogens to overcome host defenses is the modulation of host cell death. Previous observations have indicated that Yersinia pestis, the causative agent of plague disease, exhibits restricted capacity to induce cell death in macrophages due to ineffective translocation of the type III secretion effector YopJ, as opposed to the readily translocated YopP, the YopJ homologue of the enteropathogen Yersinia enterocolitica Oratio8. This led us to suggest that reduced cytotoxic potency may allow pathogen propagation within a shielded niche, leading to increased virulence. To test the relationship between cytotoxic potential and virulence, we replaced Y. pestis YopJ with YopP. The YopP-expressing Y. pestis strain exhibited high cytotoxic activity against macrophages in vitro. Following subcutaneous infection, this strain had reduced ability to colonize internal organs, was unable to induce septicemia and exhibited at least a 10(7)-fold reduction in virulence. Yet, upon intravenous or intranasal infection, it was still as virulent as the wild-type strain. The subcutaneous administration of the cytotoxic Y. pestis strain appears to activate a rapid and potent systemic, CTL-independent, immunoprotective response, allowing the organism to overcome simultaneous coinfection with 10,000 LD(50) of virulent Y. pestis. Moreover, three days after subcutaneous administration of this strain, animals were also protected against septicemic or primary pneumonic plague. Our findings indicate that an inverse relationship exists between the cytotoxic potential of Y. pestis and its virulence following subcutaneous infection. This appears to be associated with the ability of the engineered cytotoxic Y. pestis strain to induce very rapid, effective and long-lasting protection against bubonic and pneumonic plague. These observations have novel implications for the development of vaccines/therapies against Y. pestis and shed new light on the virulence strategies of Y. pestis in nature.

Show MeSH
Related in: MedlinePlus